Q: While setting a default account for new contacts is all well and good, the real issue for me is when I create a contact I want to be able to choose what account I want to put it in. Does anyone have a solution for this?
– Julien, responding to Choosing where to place new Contacts

A: Although there’s no way to choose a Contacts account during the actual creation process, you can actually determine which account a new contact goes into simply by making sure that it’s the only account selected before you create the contact. Tapping the “Groups” button in the top-left corner in the Contacts app will display a list of all of your accounts for Contacts and a list of the groups within those which support multiple contact groups on iOS.
Simply ensure that the account that you want to create your new contact is the only once selected, then tap the “Done” button and create your contact as you normally would. You can quickly select only a single contact account by tapping the “Hide All Contacts” button and then tapping the account you want to use. You can later return to the full view by tapping the “Show All Contacts” button.
It’s unfortunately a somewhat cumbersome workaround, but it will work to ensure your contacts go where you want them to.
The Default Account for new contacts specified in the iOS Settings app only applies when more than one address book source is selected in the Contacts app, or for any contacts you create from outside of the Contacts app, such as from a recent call in the Phone app, or an e-mail address in the Mail app. Sadly, this doesn’t help you much if this is the way you normally create your contacts, although you can still use the iOS clipboard to copy phone numbers and e-mail addresses into a new contact that you create manually.